Interference preventing arrangement for internal combustion engines



Nov. '21, 1939. J. DlEl' RlCH ET'AL INTERFERENCE PREVENTING ARRANGEMENTFOR INTERNAL C OMBUSTIQN ENGINES Filed Nov. 13, 1937 Fig. 7

1% v "vim ML M Hay/"AW Patented Nov. 21, 1939 UNITED STATESPATENT OFFICEINTERFERENCE PREVENTING ARRANGE- MENT ,FOR INTERNAL COMBUSTION EN- GINESJohannes Dietrich, Berlin-Charlottenburg, and

Kurt f Hagenhaus, Berlin-Siemensstadt,

Ger-

many, assignors to Siemens Apparate und Maschinen Gesellschaft mitbeschrankter Haftung, Berlin, Germany, a corporation of GermanyApplication November 13, 1937, Serial No. 174,282 -In' Germany November14, 1936 5 Claims. (01. 123-1148).

The present invention relates to an -arrangement for eliminating radiointerferences caused by theelectric ignition. apparatus of internal tionof interferences cannot be'thereby attained,

since the circuit from the spark plug is closed through the frame of thevehicle and the internal combustion engine, so that the interferingcurrents to a great extent pass through these parts and thus have anopportunity to spread. The connections from the shielding parts of theignition apparatus and the like to the frame of the vehicle are oftenvery long, the length depending upon the construction of thevehicle,'and. may

also give rise to a spreading of interfering oscillations.

It is an object of the invention to improve the protection against radiointerferences on vehicles over the above-mentioned arrangements, and,

more in particular, to prevent disturbing oscil lations from passingthrough and spreading from the frame and the engine or from groundingleads connected therewith. Other objects will tion engine of thevehicle, as well as against the other electric circuits on the vehicle.To this end, it ispreferable to individually insulate the two electrodesof the spark plug from the outer metallicsleeve of the plug so thatthere is no connection of the electrodes with the bodyoi the vehicle. Inconnecting such a double-pole spark plug with the -sparking coil, atwo-wire ignition cable is accordingly employedwhich may be providedwith a protective sheath. The ignition cable may also be designed in themanner that one conductor forms a concentric sheath around the other sothat an electric and magnetic field is created only within the cablebetween both conductors, but not so asto radiate outwardly. In theneighborhood of such ignition cables, radio receiving sets may bearranged without interferences being transmitted to the set, owing tothe absence of interfering fields outside of the conductor. when usingsuch conductors-the outer conductor in the form of a sheath may also beemployed for connecting the protective hoods of parts of the ignitionapparatus, that is to say, particularly of the shielded spark plug, theshielded distributor and of the correspondingly designed sparking coil.

While thus the spreading of interfering cur rents over the frame of thevehicle and the body of the internal combustion engine is prevented bythe complete insulation of the ignition apparatus, particularly of itshigh-voltage side, the spreading of the interfering oscillations fromcircuits connected to the ignition system may be prevented by thearrangement of filters in the-current supply leads of the ignitionsystem. A shielding between these circuits, furthermore, may be providedby arranging, for instance, I

a metallic screen between the windings of the sparking coil. Furtherdetails of the invention will be apparent from thefollowing descriptiontaken in connection with the accompanying drawing in which- Fig; 1 showsdiagrammaticallyv an arrangement according to the invention with atwo-wire ignition cable leading to the spark plug shown incross-section, and r Fig. 2 is a modified form of the invention with anignition cable whose conductors lie concentrically with respect to eachother, the spark plug connected therewith being of a type other thanshown in Fig. 1.

Referring to Fig. l, i denotes a double-pole spark plug. Both spark plugelectrodes 2 and-3, which form the spark gap, are completely insulatedby the insulator 4 from the threadedmetallic casing 5.

- The spark plug is connected to the sparking coil 6 by means Of '8.two-wire ignition cable 'I in which are inserted resistors or reactors 8in the neighborhood of the spark plug in order to prevent the spreadingof interfering oscillations set up in the spark gap over. theignitioncable 'l.

Corresponding attenuation ;means may also be arranged in the ignitioncable on. the distributorwhich for 'the sake of simplicityfisnot shown.

In the primary circuit of the sparking coil 8 is arranged in a knownmanner the breaking contact 9 in series with the-primary winding of thesparking coil and with the power source I. The, spreading of interferinghigh-frequency oscillacircuits connected to the battery Ill, as, forinstance, the lighting circuitsin the case of vehicles.

The sparking coil 6 is preferably provided with 'a protective casing l3which may be connected to one side of the high-voltage winding. In thiscase it is preferable to insulate the casing from the frame of thevehicle and of the internal combustion engine, as a completely insulatedarrangementof the ignition apparatus can only be of advantage.

In the embodiment shown in Fig. 2, the spark plug l4 consists of acentral electrode l5 surrounded by an insulatedly arranged sleeve itwhich at the same time serves. as a supply lead to the electrode J1. Theelectrodes I5 and I! as well as the sleeve l6 are insulated from theouter metallic casing "of the spark plug. To this end, two concentricinsulating sleeves l8 are provided consisting preferably of ceramicmaterial. The sleeve i6 extends also over the terminal for the centralelectrode I5 and is connected to the casing 20 of the sparking coilthrough the outer conductor IQ of the concentric ignition cable designedin the form of a sheath, whereas the inner conductor 2| of the cable isconnected to the pole of the sparking coil at the high-voltage side notconnected to the sheath. In the primary circuit of the ignitionapparatus are arranged the same devices for preventing the spreading ofinterfering oscillations over the other circuits and are designated bythe same reference numerals as in Fig. 1. Also in this case it ispreferable to prevent any passage of the interfering oscillatio'ns' tothe frame of the vehicle or the body of the internal combustion engineby insulating both conductors of the ignition cable as well as byinsulating the protective hoods of the sparking coil and the otherdevices, for instance, the distributor not shown in the drawing.

What is claimed is:

1. In an arrangement for preventing the ignition system of internalcombustion engines from causing radio disturbances, comprising anignition transformer having a primary winding, and a secondary windinginsulated from said primary winding, a bipolar cable having itsconductors connected with said secondary winding and insulated from saidengine, a spark plug having a casing mounted on said engine and bipolarelectrodes insulated from said casing and connected with saidconductors, an energizing circuit connected with said primary. winding,said circuit including a ground connection between said primary windingand said engine, shunt means for blockinghigh frequency currentsfrom'passing through said ground connection, and a conductive casingenclosing said transformer and said shunt means, said casing beinginsulated from said engine.

2. In an arrangement for preventing the ignition system of internalcombustion engines from causing radio disturbances, comprising anignition transformer having a primary winding and a secondary windinginsulated from said primary winding, a bipolar cable having itsconductors connected with said secondary winding and insulated from saidengine, a spark plug having a casing mounted on said engine and bipolarelectrodes insulated from said casing'and connected with saidconductors, an energizingcircuit connected with said primary winding,saidr ci-rcuit including a ground connection between said primarywinding and said engine, high-frequency shunt means connected acrosssaid primary winding, and a conductive casing enclosing said transformerand said shunt means, said casing being insulated from said engine andconnected with one of said secondary conductors.

3. In an arrangement for preventing the ignition system of internalcombustion engines 5 from causing radio disturbances, comprising anignition'transformer having a primary winding and a secondary windinginsulated from said primary winding, a bipolar cable having itsconductors connected with said secondary winding and insulated from saidengine, a spark plug having a casing mounted on said engine and bipolarelectrodes insulated from said casing and connected with saidconductors, impedances for attenuating high-frequency oscillations,said'impedances beingconnectedwith said conductors nearsaid electrodes,an energizing circuit connected with said primary winding, said circuitincluding a ground connection between said pri mary winding and saidengine, shunt means for blocking high frequency cur-rents from passingthrough said ground connection, and a conductive casing enclosing saidtransformer andsaid shunt means, said casing being insulated from saidengine and connected with one pole of said secondary winding.

nition system of internal combustion .engines from causing radiodisturbances, comprising an ignition transformer having a primarywinding, a secondary winding insulated from said primary winding, and ametallic screen between said primary and secondary windings, a sparkplug having a casing mounted on said engine and bipolar electrodesinsulated from said casing, a secondary circuit connected with saidsecondary winding and including said electrodes, a primary circuitconnected with said primary winding, said primary circuit having aground connection leading to said engine, shunt means for blocking highfrequency currents from passing through said ground connection, andconductive shielding means enclosing said secondary circuit, saidtransformer and said shunt means, said shielding means being insulatedfrom said engine and connected with said secondary winding.

5. In an arrangement for preventing the 1gnition system of internalcombustion engines from causing radio disturbances,- comprising anignition transformer having a primary winding,

\ a secondary winding insulated'from said primary winding, and a staticscreenbetween said primary and secondary windings, a spark plug having acasing mounted on said engine and concentric electrodes insulated fromsaid casing, a cable having two concentric conductors insulated fromsaid engine and connected between said electrodes and said secondarywinding, an energizing circuitconnected with said primary winding, saidcircuit including .a ground connection between said primary winding andsaid engine,

tion, and a conductive casing enclosing said transformer and said-shuntmeans, said casing being connected with the outer of said concentricconductors and insulated from said engine.

J OHANNES DIETRICH. KURT HAGE'NHAUS.

